This project will focus on how to delineate watersheds using two different methods. The first, using ArcGIS Pro and StreamStats, and the other, using ndhdPlus Tools in R.
The packages required for this lesson include:
-Tidyverse, in order to use pipes
-mapview, in order to map the delineated watersheds
-nhdplusTools, to delineate the watershed
For this method of delineating watersheds, we will be using StreamStats, a program run by the USGS which allows flowlines to be selected, and returns stats on the chosen watershed. The site that we are going to be using for our watershed delineation is in Greeley, Colorado.
Station ID: 06752500
Station Name: CACHE LA POUDRE RIVER NEAR GREELEY, CO.
Latitude: 40.41776
Longitude: -104.64
Go to “search for a place”, enter the station ID, and select Colorado as the State. This will bring you to the part where you delineate your watershed.
Click the Delineate button and then click on one of the blue pixels near our site. This process may take a few minutes. (Reference Q2_Image)
Before we collect the data for Arc select DRNAREA under basin characteristics, continue, and open report. How large is the drainage area for this watershed?
Once this process is completed you will see a view of the watershed that we are delineating.
Create a new ArcGIS project and import the data from StreamStats by right clicking Map under drawing order and select add data. Navigate to your layers file location and select the two.shp files. Now we have our data in Arc!
We now want to change the projection of our map so we can take more accurate measurements of this watershed. To do this you will want to right-click on map go to Properties – Coordinate Systems – Projected Coordinate System – State Plane – NAD 1983 (2011) (Meters) – StatePlane Colorado North FIPS 0501 (Reference Q6_Image)
Now that we have changed the coordinate system, we can now calculate the area for this watershed. To do this you will select Measure under the map tab, select Measure Features, and click on the watershed boundary polygon (make sure that you select Metric for the units to be displayed in). What is the area that you found? How does the area differ from the drainage areacollected from Stream Stats?
#Downloading the data Using the ndhPlus Tools, download the HUC8 for the Cache la Poudre Watershed.
# Download the huc 8 for the Poudre River using its USGS code
poud <- get_huc8(id = "10190007" )
# This will give you an outline of the Poudre River watershed, with metadata
Now that the data has been downloaded, we can add the flowlinesof the watershed, similar to the flowlines in StreamStats.
# Next, we can get the flowlines (all the streams) in the watershed
poud_flowlines <- get_nhdplus(AOI = poud,
realization='flowline') # selects flowline in the search
## Found invalid geometry, attempting to fix.
Finally, plot your delineated watershed.
#Plot your watershed using mapview!
mapview(poud_flowlines, color = "darkblue") + mapview(poud, color = "lightblue")